Synthesis of a diamino substituted terphenyldivinyl chromophore

Article abstract of DOI:10.3390/molecules14062111

(E, E)-1,4-bis(4'-aminostyryl)-2,5-bis(octyloxy)-benzene (6) and its derivative (E, E)-1,4-bis(4'-acetamidostyryl)-2,5-bis(octyloxy)-benzene (7) were synthesized and characterized after alkylation, bromomethylation, Horner-Emmons reaction and reduction fr

Full text of DOI:10.3390/molecules14062111

Molecules 2009, 14, 2111-2117; doi:10.3390/molecules14062111
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Synthesis of a Diamino Substituted Terphenyldivinyl
Chromophore
Zhen-Ting Du 1,*, Ru Liu 1, Jun-Ru Wang 1 and An-Pai Li 2,*
1
College of Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China;
E-mails: liuru75@gmail.com (R.L.), wangjr07@163.com (J-R.W.)
2
Synthetics Technologica Pte Ltd, 3 Phillip Street, #18-00 Commerce Point, 048693, Singapore;
E-mail: anpaili@sina.com (A-P.L.)
* Author to whom correspondence should be addressed; E-mail duzt@nwsuaf.edu.cn;
Tel.: +86-29-87092226; Fax: +86-29-87092226
Received: 24 April 2009; in revised form: 1 June 2009 / Accepted: 3 June 2009 /
Published: 10 June 2009
Abstract: (E,E)-1,4-bis(4'-aminostyryl)-2,5-bis(octyloxy)-benzene (6) and its derivative
(E,E)-1,4-bis(4'-acetamidostyryl)-2,5-bis(octyloxy)-benzene (7) were synthesized and
characterized after alkylation, bromomethylation, Horner-Emmons reaction and reduction
from hydroquinone. In order to gain more molecular electronic data, HOMO and LUMO
of compound 6 have been calculated by Gaussian 03 W.
Keywords: chromophore; energy transfer; synthesis; terphenyldivinyl
Introduction
As we all know, photosynthesis is the most important way on which all the lives in our planet
depend directly or indirectly. Now, photosynthesis has been understood as a series sequence of energy
and charge transfer in plants or microorganisms. Some photo-voltaic processes are designed based on
mechanism of photosynthesis [1-3]. However, there is still a necessity to design and discover new
chromophores to meet the need in research of charge or energy transfer. At the same time, organic
light-emitting devices (OLED) employing organic chromophores as emitters have been the focuses of
considerable interest because of their possible application as display for mobile phones, personal
computers, and television [4,5]. Oligophenylvinyl [6-9] is a common chromophore used in study of

Molecules 2009, 14
2112
energy transfer or in OLED. A diamino substituted oligophenylvinyl (E,E)-1,4-bis(4'-aminostyryl)-2,5-
dimethoxybenzene (BDB) have been reported by Wu [10], but the synthetic process was not published.
As shown in Figure 1, we have designed a polymer consist of terphenyldivinyl and perylene
tetracarboxylic anhydride [11-16] which through double imide bond in our future research.
Figure 1. Designed polymer with terphenyldivinyl and perylene moiety.
Because of the low solubility of perylene moiety in common solvent, the long carbon chain was
introduced. So oligophenylvinyl chromophore 6 and its acetylated derivative 7 were devised and
synthesized. Herein, we describe the synthesis of these series chromophores and the results of
theoretical computation.
Results and Discussion
As shown in Scheme 1, the long alkyl chain ether in the middle phenyl ring can increase the
solubility of the chromophores in common solvent considerably, the terminal amino group is a
versatile functional group to link with other chromophores, and meanwhile, the O and N substituted
ones can elevate the HOMO level.
Scheme 1. Synthesis of 6 and 7.
Reagents and conditions: (a): KOH, n-C8H17Br, DMSO, reflux, 80oC, 75%; (b): 40% HBr, HOAc,
(CH2O)n, reflux, 71%; (c): P(OEt)3, reflux; (d) t-BuOK, 4-nitrobenzyladehyde, THF, 74% for two
.
steps; (e) I2(cat.), Tol., reflux, 95%; (f) SnCl2 2H2O, EtOH, EtOAc, 83%; (g): AcCl, Et3N, DMAP,
96%.

Molecules 2009, 14
2113
The synthetic strategy employed for the synthesis of 7 was based on the Horner-Emmons reaction.
Hydroquinone was used as starting material, which was alkylated in DMSO with C8H17Br in the
presence of KOH, and then it was subsequently treated with conc. HBr and paraformaldehyde, to give
a benzyl bromide derivative. Compound 3 was reacted with P(OEt)3 to give the phosphonate 4. After
reaction of 4-nitrobenzyladehyde and the phosphonate 4, a mixture of cis and trans isomers was
obtained. In order to get all trans product, a catalytic isomerization of the mixtures was performed in
the presence of iodide in toluene to convert the cis isomers to compound 5’. A tin (II) chloride
reduction of the nitro groups [17] afforded diamino substituted terphenyldivinyl derivative 6.
Compound 6 was subjected to a conventional acetylation process to give compound 7.
Moreover, to gain insight into the electronic properties of our target molecular, its molecular
geometry was fully optimized at the B3LYP/6-31G level 10 using Gaussian 03 package. As shown in
Figure 2, the contour of HOMO and LUMO of compound 6 was given after computational calculation.
The HOMO and LUMO were condensed mostly on middle benzene ring, and the long alkyl chains
were distributed symmetrically. The levels of HOMO and LUMO were -4.41eV and -1.20eV,
respectively.
Figure 2. HOMO and LUMO of 6 at the B3LYP/6-31G.
The absorption and emission spectrum were also evaluated. The absorption peak of compound 6
and 7 are at 401 nm and 397 nm, and the max emission are at 466 nm and 458 nm, respectively. This
emission wavelength indicated that it can be cooperated with perylene moiety as donor [16].
Figure 3. The absorption and emission of 6 and 7 in CH2Cl2.

Molecules 2009, 14
2114
Experimental
General
1
13
The H-NMR and C-NMR data were recorded in CDCl3 solution with Bruker AM-200 or AM-
400 MHz spectrometers. The chemical shifts are reported in ppm relative to TMS or CDCl3. Column
chromatography were generally performed on silica gel (200-300 mesh) eluting with petroleum
ether:EtOAc (100:1-10:1 v/v) and TLC inspections on silica gel GF254 plates with petroleum
ether:EtOAc ( 20:1-5:1 v/v ) if not noted otherwise.
1,4-bis(Octyloxy)benzene (2): Under Ar, a mixture of hydroquinone (55.0 g, 0.5 mol), KOH (67.2 g,
1.2 mol) and octyl bromide (251.0 g, 1.3 mol) in DMSO (400 mL) was stirred for 48 hours at 80oC.
after the reaction completion and cooling, the reaction mixture was poured into water (2000 mL) with
stirring, the precipitate was collected and washed with water (300 mL) and ether/petroleum ether (1:1,
1
3×50 mL) and the product (125 g, 75%) was used in the next step without further purification. H-
NMR: 0.91 (t, J=6.6 Hz, 6H), 1.29-1.33 (m, 16H), 1.43-1.46 (m, 4H), 1.74-1.79 (m, 4H), 3.92 (t,
J=6.6 Hz, 4H), 6.84 (s, 4H).
1,4-bis(Bromomethyl)-2,5-bis(octyloxy)benzene (3): A mixture of 1,4-bis(octyloxy)benzene (6, 33.4 g,
0.1 mol), paraformaldehyde (10.8 g, 0.36 mol), HOAc (80 mL) and HBr (40%, 50 mL) was refluxed
for 24 hours; after cooling, the precipitate was collected and washed with water. The compound (40 g,
1
71%) was used for the next step without further purification. H-NMR: 0.93 (t, J=6.6 Hz, 6H), 1.32-
1.37 (m, 16H), 1.50-1.53 (m, 4H), 1.84-1.87 (m, 4H), 3.98 (t, J=6.6 Hz, 4H), 4.54 (s, 4H), 6.87 (s, 2H).
Tetraethyl (2,5-bis(octyloxy)-1,4-phenylene)bis(methylene)diphosphonate (4): A mixture of compound
3 (5.0 g, 10mol) and triethyl phosphite (4.1 g, 0.025 mol) was refluxed for 12 hours, and then the
volatiles were stripped off by oil pump. The residue of the desired diphosphonate 4 was used directly.
1,4-bis(4'-Nitrostyryl)-2,5-bis(octyloxy)-benzene (5): Under an atmosphere of Ar, t-BuOK (2.47 g, 22
mmol) was added portionwise at 0oC to a solution of the residue of 4 mentioned above dissolved in
anhydrous THF (30 mL). The mixture was stirred at this temperature for 2 h, then a solution of 4-
nitro-benzaldehyde (3.33 g, 22 mmol) in anhydrous THF (10 mL) was added. The reaction mixture
was stirred at 0oC for 2 hours, and then at 25oC for an additional 4 hours. Finally the mixture was
quenched with water, the volatiles were evaporated first, then the aqueous phase was extracted with
ethyl acetate (3×50 mL), The combined organic extracts were washed with brine (2×10 mL), dried
over anhydrous sodium sulfate and evaporated, the product (4.65 g, 74%) after flash column
chromatography was obtained as a mixture of cis and trans isomers 5.
(E,E)-1,4-bis(4'-nitrostyryl)-2,5-bis(octyloxy)-benzene (5’): To a solution of the crude compound 5
(4.50 g, 7.1 mmol) in toluene (75 mL) was added I2 (90 mg, 0.355 mmol), then the mixture was
1
refluxed for 3 days and monitored by H-NMR. After completion, the mixture was washed with
sodium sulfite, water, brine (10 mL) and dried over anhydrous sodium sulfate. Purification by column

Molecules 2009, 14
2115
chromatography afforded (E,E)-1,4-bis(4'-nitrostyryl)-2,5-bis(octyloxy)-benzene (5’, 4.27 g, 95%) as a
red solid. 1H-NMR: 0.88 (t, J=6.8 Hz, 6H), 1.27-1.43 (m, 16H), 1.51-1.57 (m, 4H), 1.86-1.91 (m, 4H),
4.07 (t, J=6.8 Hz, 4H), 7.12 (s, 2H), 7.21 (d, J=16 Hz, 2H), 7.61(d, J=8 Hz, 4H), 7.62 (d, J=16 Hz, 2H),
8.21(d, J=8 Hz, 4H). 13C-NMR: 14.56, 23.06, 26.64, 29.65, 29.71, 29.72, 32.12, 69.44, 110.42, 123.78,
126.34, 126.43, 126.59, 127.53, 143.82, 146.03, 150.84.
(E,E)-1,4-bis(4'-aminostyryl)-2,5-bis(octyloxy)-benzene (6): To a solution of compound 5’ (1.5 g 2.4
mmol) in ethanol (20 mL) and ethyl acetate (20 mL), SnCl2 dihydrate (15 g, 80 mmol) was added, and
the reaction mixture was refluxed for 8 hours. After completion, water (50 mL) was added and the
reaction mixture extracted with ethyl acetate (3×50 mL). The combined organic extracts were washed
successively with water and brine, dried over anhydrous sodium sulfate and evaporated, After
purification by column chromatography to afford (E,E)-1,4-bis(4'-aminostyryl)-2,5-bis(octyloxy)-
1
benzene 6 (1.12g, 83%) as red solid. H-NMR: 0.88 (t, J=7.2 Hz, 6H), 1.27-1.43 (m, 16H), 1.51-1.57
(m, 4H), 1.86-1.91 (m, 4H), 3.74 (s, 4H), 4.03 (t, J=6.4 Hz, 4H), 6.65(dt, J=8.4 Hz, J=2 Hz, 4H), 7.03
(d, J=16.8 Hz, 2H), 7.07 (s, 2H), 7.26 (d, J=16.8 Hz, 2H), 7.33(dt, J=8.4 Hz, J=2 Hz, 4H); 13C-NMR:
14.60, 23.09, 23.66, 29.67, 29.78, 29.88, 32.15, 69.63, 110.03, 114.90, 119.59, 126.40, 127.30, 127.98,
128.38, 145.33, 150.24.
(E,E)-1,4-bis(4'-Acetamidostyryl)-2,5-bis(octyloxy)-benzene (7): To a solution of compound 6 (568 mg,
1 mmol), Et3N (1 mL) and DMAP (12 mg, 1 mmol) in CH2Cl2 (10 mL), AcCl (200 mg, 2.5 mmol) was
added and the reaction mixture was stirred at room temperature and monitored by TLC. After
completion of the reaction, the mixture was quenched with water and extracted with CH2Cl2 (3×30
mL), then the combined organic extracts were washed successively with water, brine, dried over
anhydrous sodium sulfate and evaporated, purification by column chromatography afforded compound
1
7 (626 mg, 96%) as a red solid. H-NMR: 0.83 (t, J=7.2 Hz, 6H), 1.17-1.38 (m, 16H), 1.57-1.63 (m,
4H), 1.86-1.91 (m, 4H), 2.05 (s, 6H), 3.98 (t, J=6.4 Hz, 4H), 6.95(s, 2H), 7.42 (d, J=8.4 Hz, 4H), 7.43
(d, J=16 Hz, 2H), 7.56 (d, J=16 Hz, 2H), 7.64(d, J=8.4 Hz, 4H), 9.99(s, 2H); 13C-NMR: 14.62, 23.19,
23.64, 24.11, 29.67, 29.78, 29.88, 32.15, 69.67, 110.17, 115.10, 120.35, 126.58, 127.33, 127.98,
128.61, 145.96, 151.82, 168.91.
Conclusions
In summary, we have designed and synthesized a new diamino substituted Oligophenylvinyl
chromophore (E,E)-1,4-bis(4'-aminostyryl)-2,5-bis(octyloxy)-benzene (6) and its derivative (E,E)-1,4-
bis(4'-acetamidostyryl)-2,5-bis(octyloxy)-benzene (7). At the same time, we have examined the
HOMO and the LUMO levels after theoretical calculations. Further application is in progress.
Acknowledgements
Financial support from Program for Excellent Young Talents in Northwest A&F University
(2111020712) as well as the National Natural Science Foundation of China (20802058) is greatly
appreciated. I am indebted to Professor Hou and Professor Yin for their detailed discussions on the
utilization of Gaussian for calculations.

Molecules 2009, 14
2116
References and Notes
1. Baik, C.; Kim, D.; Kang, M.S.; Kang, S.O.; Ko, J.; Nazeeruddin, M.K.; Gratzel, M. Organic dyes
with a novel anchoring group for dye-sensitized solar cell applications. J. Photochem. Photobiol.
A 2009, 201, 168-174.
2. Yum, J.H.; Hagberg, D.P.; Moon, S.J.; Karlsson, K.M.; Marinado, T.; Sun, L.C.; Hagfeldt, A.;
Nazeeruddin, M.K.; Gratzel, M. A Light-Resistant Organic Sensitizer for Solar-Cell Applications.
Angew. Chem. Int. Edit. 2009, 48, 1576-1580.
3. Yum, J.H.; Jung, I.; Baik, C.; Ko, J.; Nazeeruddin, M.K.; Gratzel, M. High efficient donor-
acceptor ruthenium complex for dye-sensitized solar cell applications. Energy Environ. Sci. 2009,
2, 100-102.
4. Tang, C.W.; Vanslyke, S.A. Organic electroluminescent diodes. J. Appl. Phys. 1987, 51, 913-915.
5. Mason, M.G.; Hung, L.S.; Tang, C.W.; Lee, S.T.; Wong, K.W.; Wang, M. Characterization of
treated indium-tin-oxide surfaces used in electroluminescent devices. J. Appl. Phys. 1999, 86,
1688-1692.
6. Jin, J.Y.; Jin, Z.Z.; Xia, Y.; Zhou, Z.Y.; Wu, X.; Zhu, D.X.; Su, Z.M. Design and synthesis of 1,4-
bis[4-(1,1-dicyanovinyl)styryl]-2,5-bis(alkoxy)benzenes as red organic electroluminescent PPV
analogs. Polymer 2007, 48, 4028-4033.
7. Cacialli, F.; Feast, W.J.; Friend, R.H.; de Jong, M.; Lovenich, P.W.; Salaneck, W.R. Synthesis
and characterisation of poly(distyrylbenzene-block-hexa(ethylene oxide)) and its fluorinated
analogue-two new block copolymers and their application in electroluminescent devices. Polymer
2002, 43, 3555-3561.
8. Kimoto, A.; Masachika, K.; Cho, J.S.; Higuchi, M.; Yamamoto, K. Synthesis and
electroluminescence properties of novel main chain poly(p-phenylenevinylene)s possessing
pendant phenylazomethine dendrons as metal ligation sites. Chem. Mater. 2004, 16, 5706-5712.
9. Kimura, M.; Sato, M.; Adachi, N.; Fukawa, T.; Kanbe, E.; Shirai, H. Poly(p-phenylene vinylene)s
wrapped with 1,3,5-phenylene-based rigid dendrons. Chem. Mater. 2007, 19, 2809-2815.
10. Wu, C.Y.; Tian, D.H.; Feng, Y.; Polak, P.; Wei, J.J.; Sharp, A.; Stankoff, B.; Lubetzki, C.; Zalc,
B.; Mufson, E.J.; Gould, R.M.; Feinstein, D.L.; Wang, Y.M. A novel fluorescent probe that is
brain permeable and selectively binds to myelin. J. Histochem. Cytochem. 2006, 54, 997-1004.
11. Abbel, R.; Grenier, C.; Pouderoijen, M.J.; Stouwdam, J.W.; Leclere, P.; Sijbesma, R.P.; Meijer,
E.W.; Schenning, A. White-Light Emitting Hydrogen-Bonded Supramolecular Copolymers Based
on pi-Conjugated Oligomers. J. Am. Chem. Soc. 2009, 131, 833-843.
12. Shanks, D.; Preus, S.; Qvortrup, K.; Hassenkam, T.; Nielsen, M.B.; Kilsa, K. Excitation energy
transfer in novel acetylenic perylene diimide scaffolds. New J. Chem. 2009, 33, 507-516.
13. Takahashi, M.; Ichihashi, Y.; Nishizawa, N.; Ohno, S.; Fujit, N.; Yamashita, M.; Sengoku, T.;
Yoda, H. Construction of light-harvesting reverse micelles in nanoscopic dimensions. J. Photoch.
Photobio. A 2009, 203, 56-63.
14. Wang, H.Y.; Pu, K.Y.; Huang, S.; Liu, F.; Peng, B.; Wei, W. Alternating copolymers based on
perylene bisimide and oligo(p-phenylene ethynylene) units: Synthesis, characterization, and
photoinduced energy and electron transfer processes of a new class of donor-acceptor systems.
React. Funct. Polym. 2009, 69, 117-123.

Molecules 2009, 14
2117
15. Liu, Y.; Yang, C.H.; Li, Y.J.; Li, Y.L.; Wang, S.; Zhuang, J.P.; Liu, H.B.; Wang, N.; He, X.R.; Li,
Y.F.; Zhu, D.B. Synthesis and photovoltaic characteristics of novel copolymers containing
poly(phenylenevinylene) and triphenylamine moieties connected at 1,7 bay positions of perylene
bisimide. Macromolecules 2005, 38, 716-721.
16. Syamakumari, A.; Schenning, A.P.H.J.; Meijer, E.W. Synthesis, optical properties, and
aggregation behavior of a triad system based on perylene and oligo(p-phenylene vinylene) units.
Chem. Eur. J. 2002, 9, 3353-3361.
17. Bellamy, F.D.; Ou, K. Selective reduction of aromatic nitro compounds with stannous chloride in
non acidic and non aqueous medium. Tetrahedron Lett. 1984, 25, 839-842.
Sample Availability: Samples of the compounds 1 to 7 are available from the authors.
© 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.
This article is an open-access article distributed under the terms and conditions of the Creative
Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).